Glyph group is flattened in one-to-one substitution when input is group

[kalapi]

Fez code is:

Feature ordn {
    Substitute [A a] -> ordfeminine <<latn/dflt>>;
    Substitute [O o] -> ordmasculine <<latn/dflt>>;
};

Output is:

lookup Routine_10 {
    lookupflag 0;
    ;
    sub [A O] by [ordfeminine ordmasculine];
} Routine_10;